1. Field of the Invention
The present invention relates to the field of radiation and immunomodulation of tumor cells.
2. Description of the Relevant Art
Upon diagnosis of early stage breast cancer, patients are faced with the choice between having 1) a mastectomy (total removal of the breast) or 2) breast-preserving surgery (lumpectomy) and radiation therapy (RT), each resulting in comparable local recurrence rates and overall survival [Reference 1, 2]. RT decreases the risk of local recurrence by ˜70%, and remains the standard treatment after lumpectomy [Reference 1]. The typical course of RT after lumpectomy consists of daily treatments of 2.0 Gy per fraction to a total dose of 50-60 Gy. This regimen has largely been derived empirically over time, and has been shown to result in excellent outcomes, with minimal morbidity [Reference 3]. However, the entire course usually requires 6-7 weeks of daily treatments, which often imposes a burden of time and cost that are significant obstacles for many women who are then left with little better alternative than mastectomy. In fact, a survey by the American College of Surgeons reported that in 1999, the majority of women in the United States who were candidates for breast-preservation (lumpectomy plus RT) were undergoing mastectomy! [Reference 4] Indeed, the distance and accessibility to RT centers has been shown to be a significant barrier to treatment [Reference 5]. Thus, in recent years, different strategies have been used to decrease the total time required for RT; these include accelerating treatment (increasing the daily fraction or dose), decreasing treatment volumes and using different RT sources (e.g.) brachytherapy, or the in situ placement of radioactive sources) [Reference 6-9]. These are still investigational, and it may take several years before the optimal approach is determined, in part because late effects of RT may not occur for several years. In addition, the use of accelerated treatment, or larger doses per day, has been shown to increase the risk for late effects [Reference 10, 11]. Thus, while the outcomes of clinical trials are ongoing to test these approaches against one another (a large cooperative trial is planned to begin in the U.S. in 2004, but will not reach maturity for 11 years after accrual, ˜2016-2017), it is imperative to investigate novel biologic approaches to improving RT for breast cancer that will increase the efficacy of tumor eradication, while decreasing normal tissue toxicity. This strategy will conceivably lead to decreasing RT doses, making RT less cumbersome and more accessible for patients.
Breast cancer treatment has historically consisted of targeting cancer cells using cytotoxic agents such as chemotherapy and radiation. With the growing recognition that tumors are comprised not only of cancerous cells, but a tumor-promoting microenvironment consisting of many cell types, extracellular matrix (ECM) and stromal factors, novel biologic therapies directed specifically at these targets are being considered and developed. In addition, the ability of tumor cells to adhere to the ECM modify responsiveness to ionizing radiation (IR) [Reference 12] and cell-cell and cell-ECM interactions have been shown to modulate radio sensitivity [Reference 13, 14]. We have previously shown that radiation profoundly influences the ability of mammary epithelial cells to form normal interactions with other cells and ECM [Reference 15]. In particular, single doses of IR resulted in a persistent increase and aberrant expression of β1 integrin, a receptor that is critical in mediating cell-ECM interactions; this observation has been corroborated by others in several tumor cell types [Reference 16, 17]. Furthermore, the increased expression of β1 integrin in response to IR has been shown to be associated with increased radioresistance. β1 integrin belongs to a family of transmembrane receptors that directly mediate cell-ECM interactions (reviewed in [Reference 18, 19]) and are critical in maintaining normal tissue architecture and function.
The family of integrin receptors comprises 18α and 8β subunits that may heterodimerize with each other in various combinations to confer ligand and substrate specificity; the class of β1 integrin receptors is pivotal in signaling cell communication with the microenvironment that governs a wide variety of cellular events including cell growth, apoptosis, adhesion, migration, and differentiation. As is true for many signaling receptors, β1 integrin function depends on the context in which signaling takes place and is different in normal cell and malignant cell context.
In breast cancer, β1 integrin has been implicated in malignant progression in human tissue-based studies as well as in vitro and in vivo models of breast cancer. Studies in human breast cancers, largely based on retrospective analyses of paraffin embedded tissue, indicate that specific heterodimers of β1 integrin are aberrantly expressed as carcinomas become increasingly undifferentiated (Reviewed by Shaw [Reference 20]). The role of β1 integrin as a prognostic factor remains unclear, however, existing data are consistent in describing an association been altered β1 integrin expression and malignant progression. Among in vitro models of breast cancer, β1 integrin has been associated with maintenance of normal tissue architecture [Reference 21, 22], and xenograft models have implicated its role in metastasis [Reference 23, 24].
The primary functional roles of β1 integrin in breast cancer progression have linked β1 integrin expression and signaling associated with growth and differentiation [Reference 21, 25]. These studies indicate that the relative levels of β1 integrin in relationship to other cooperative signaling pathways are important in mediating normal cell-ECM interactions, and the ability of cells to differentiate in 3-dimensional tissue culture. In addition, an emerging body of evidence indicates that β1 integrin plays a significant role in mediating resistance to cytotoxic chemotherapies, not only in breast cancer, but several other cancer cell types, by up-regulating cell survival signals. In particular, β1 integrin mediated adhesion to the ECM has been associated with resistance to cell death [Reference 12, 16, 17, 26], and a cytoprotective effect has been observed against DNA-damaging agents in hematologic malignancies, and lung and breast cancers. Recent studies in vivo using a β1 integrin inhibiting peptide enhanced the effect of 5-FU chemotherapy against colon cancer xenografts [Reference 27].
Antibodies to integrins, and, in particular, β1 integrin, useful in the practice of the present methods, are known in the art. See Bissell et al. U.S. Pat. No. 6,123,941 for a description of reverting malignant phenotype in cancer cells through application of anti-β1 integrin antibody AIIB2. Anti beta-1 integrins against the CD-29 epitope are available from Research Diagnostics, Inc., Flanders, N.J. Another anti-β1 integrin antibody is CSAT, available from the University of Iowa Hybridoma Bank. Another commercially available anti-β1 integrin antibody is 4B7R, a Murine IgG1kappa antibody available from Ancell Immunology Research Products.
Other antibodies (not anti-beta-1) are known for the treatment of cancer, e.g. Herceptin™ antibody (rastuzumab). This antibody attaches to breast cancer cells which possess a receptor site called HER2/neu. RT has been suggested for use with Herceptin, but little data exist as to the desirability of such combination treatments.
RT is generally offered to breast cancer patients to rid the body of any microscopic cancer cells that may remain near the area where the cancer was originally receptor. Chemotherapy of cancer is often combined with radiation therapy. Although there have been efforts to combine biologic agents with radiotherapy, including monoclonal antibodies against the epidermal growth factor receptor (EGFR) in head and neck cancers, and lung carcinomas, little is known about the safety or efficacy of such treatments.
The usual course of RT includes daily treatments five days a week for five to seven weeks. Each session generally lasts an hour or less. Radiation therapy works by causing changes at the molecular level in tissues where the radiation beam is targeted. Giving all the radiation needed at one time would cause significant and irreparable damage not only to cancer cells, but also to normal cells. However, giving small doses of radiation each day enables the majority of healthy cells to repair any damage, while rendering cancer cells inactive.
In combining the present anti-integrin and radiation treatments, other known radiation therapies may be employed. One possibility is to administer the radiation as intraoperative radiation therapy. Another possibility is to administer the radiation through radioisotopes coupled to the anti-integrin agent. As another possibility, high-dose rate brachytherapy, which is a new form of internal radiation therapy, may be employed. This aggressive, comprehensive approach to cancer treatment frequently uses internal radiation therapy for cancers of the lung, breast, prostate, rectum, cervix, and uterus. Brachytherapy is a quicker, more effective way to give radiation therapy treatments. Brachytherapy as a radiation therapy places the radiation in the tumor, tightly concentrated within the site of the cancer. This radiation therapy technique allows that the maximum radiation dose is received where it is needed most, while allowing little radiation to effect the surrounding healthy tissue. In many cases, brachytherapy is an effective radiation therapy alternative to surgical removal of a tumor and the affected organ, and may be used in connection with the present methods.